One very popular type of printing device is the inkjet printer. Some inkjet printers use a replaceable fluid container to supply ink and/or other fluids to a fluid ejection mechanism to print onto a medium. The fluid container and fluid ejection mechanism are sometimes integrated together into a single replaceable unit that may be referred to as a pen or print cartridge. The fluid ejection mechanism may include, for example, a printhead that selectively deposits ink or other fluids onto a print medium, such as paper, through an array of nozzles. Such fluid ejection may be initiated in the printhead, for example, using thermal or piezoelectric action.
A fluid container may include one or more internal chambers that act as reservoirs for one or more fluids. A fluid holding member may be arranged within a chamber to hold the fluid in a manner that allows it to be selectively ejected through the printhead. The fluid holding member provides a backpressure that usually prevents the fluid from simply draining or drooling out of the printhead nozzles. By way of example, certain fluid holding members include fluid-absorbing foam material.
Fluid stored in the fluid holding member may be provided to the printhead through a fluid conduit. The fluid conduit, which may be referred to as a standpipe, extends into the chamber and provides an opening that contacts a surface of the fluid holding member. The fluid conduit may also include a filter or screen in contact with the fluid holding member.
The fluid container may also include an air vent that allows air pressure within a chamber to equalize or otherwise adjust with the external atmosphere's pressure. Such an air vent also allows for additional air to enter into the chamber during printing as the fluid therein is consumed through ejection.
Air or other gas that is trapped or otherwise held inside the fluid container may affect the operation of the fluid container as the pressure of the trapped air changes. For example, in certain print cartridges increased pressure of trapped air may affect the backpressure provided by the fluid holding member such that fluid may leak or drool out of the printhead.